Method of producing imaged spirit master directly from original



0d. 11, 1966 P. G. KALMAN ET L 3 METHOD OF PRODUCING IMAGED SPIRIT MASTER DIRECTLY FROM ORIGINAL Filed Dec.

FIGw .1

FIG. 2

FIG. .3

INVENTORfi Pefer G. Kev/mam 3,278,323 ME'HIQD F PRODUCING Ill/[AGED SPIRIT MAdTER DIRECTLY FROM DRIGINAL Peter G. Kalman, London, England, and Richard A. Fehlherg, Mundeiein, llll., assignors to A. B. Dick Company,

Niles, llll., a corporation of Illinois Filed Dec. 26, 1963, Ser. No. 333,542 8 Claims. (Cl. 117-175) This invention relates to the production of an imaged spirit master and it relates more particularly to the method and means for the development of a latent electrostatic image and to the production of an imaged master thereof from which multiple copies of good copy quality can be produced.

To the present, numerous techniques have been developed for the production of a latent electrostatic image by a dry process from an original or other sources of information. One such technique makes use of a layer of a photo-conductive material, such as a selenium plate, which is supplied with a surface charge by corona discharge from a source of electrical excitation and wherein portions of the charge are wiped out by exposure to light to leave a latent electrostatic image on the surface of the plate, as in the process known to the trade as the Xerox process described in the Carlson Patent No. 2,297,691, or the Electrofax process of RCA.

In another technique, referred to in the trade as the Videograph process, described in Patents No. 3,075,859, No. 2,996,573, or No. 2,879,422, an original is scanned by suitable television scanning means to generate an electrical signal which is transmitted to a cathode ray tube which emits a discharge from wires extending through the face of the tube for deposition of an electrostatic charge on a dielectric writing medium displaced between the face of the tube and a suitable ground whereby a latent electrostatic image corresponding to the original is formed on the surface of the dielectric writing medium. Instead of receiving its signals from a scanner, the cathode ray tube may be signalled by electronic read-out devices from electronic data storage means and the like.

In a more recent technique, such latent electrostatic images can be developed on elements identified in the trade as electrets, wherein the electret is formed of a photo-conductive phosphor which can be polarized and exposed for the development of a more permanent latent electro-image by the process described by Kalman and Rennert in an article entitled Data Storage and Display With Polarized Phosphors, Electronics, August 28, 1959, pages 39-41; or in which the electret can be charged solely by exposure to high voltage in a DC. field for electron movement followed by exposure to develop the electrostatic image, as described in the copending application of Kalman, Serial No. 333,540, filed December 26, 1963,

and entitled Electro-Electret and Method for Imaging Same.

In all of these processes and techniques, the latent electrostatic image is developed with a suitable toner comprising a pigment powder mixed with a carrier which is either caused to flow over the imaged surface as dry granules for retention of pigment powder by the areas retaining the electrostatic charge or in which the toner is suspended in a suitable liquid carrier with which the surface is contacted whereby pigment powder is retained only by the electrostatic charge forming the latent image. In the dry development of the image, the pigment powder is set by heat sufficient to cause fusion or softening of the thermoplastic or resinous carrier or by solvent while, in the liquid toner the pigment powder may be set by heat or solvent or preferably by resinous binder dissolved in small proportions in the liquid carrier and which sets the image upon removal of the diluent. In the systems described, the pigment powder can be set in the manner nited States Patent 0 "cc 3,278,323 Patented Oct. 11, 1966 described on the surface on which it is deposited or it can be transferred to a suitable copy sheet to free the photo-conductive layer or electret for re-use in image development.

In either event, the copy that is produced constitutes a single copy. Processes have been developed wherein the developing material comprises a waxy component which is ink receptive and water repellent whereby trans fer of the developed image onto the surface of a litho graphic plate will produce an imaged lithographic plate from which multiple copies can be secured by lithographic reproduction.

It is desirable to be able to make use of the latent electrostatic image formed by whatever process of the type described to produce an imaged spirit master from which multiple copies can be produced by the much simpler and less expensive spirit duplicating means and it is an object of this invention to provide a method and means for accomplishing the same.

These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, an embodiment of the invention is shown in the accompanying drawing, in which- FIG. 1 is a schematic top plan view of a latent electrostatic image in the photo-conductive layer of electret on which it is formed;

FIG. 2 is a top plan view of the element shown in FIG. 1 with the image developed in accordance with the practice of this invention;

FIG. 3 is a schematic sectional elevational view of the arrangement of elements for transfer of the developed image to the surface of a spirit master; and

FIG. 4 is a top plan view of the imaged master prepared in accordance with the practice of this invention.

It has been found that formulation of the pigment powder to contain a spirit soluble dyestulf, such as crystal violet, does not automatically result in the production of an image from which multiple copies can be produced because the dyestuff apparently is not available for leaching from the imaged master for transfer to the surfaces of the wetted copy sheets brought into surface contact with the imaged master in accordance with conventional spirit duplicating techniques.

It has been found, in accordance with the practice of this invention, that the desired results can be achieved when the spirit soluble dyestuif, in finely divided form, is embodied in a physical mixture with particles of a material Which is capable of acquiring a charge opposite that of the latent electrostatic image for attraction to the latent electrostatic image for the development thereof whereby upon transfer to the surface of the spirit master, the dyestulf will be retained by the particulate material on the surface of the master for image retention but wherein the dyestuff will be sufficiently free of the particulate material for solution where-by dyestuif can be leached from the imaged master to the wetted surfaces of the copy sheets brought into contact therewith.

For this purpose, it is desirable to make use of a carrier which can take a charge sufiicient for preferential attraction to the latent electrostatic image developed on the dielectric coating or electret and which is effective to bond the finely divided spirit soluble dyestuif physically mixed therewith to hold the particles on the surface of the master without blocking the particles from access for solution by the alcohol and/ or water with which the copy sheets are wet.

The following will represent a formulation suitable for the practice of this invention:

Example 1 parts by weight carnauba wax mesh or less) 10 parts by weight crystal violet in finely divided form The materials are physically mixed to form the developing powder.

When applied to the surface of an element 12 containing a latent electrostatic image 14, the carnauba Wax will be attracted to the charged areas and the crystal violet will be retained in the proportion present in the mixture, either by physical entrainment with the particles of carnauba wax or by clinging to the surfaces thereof.

In the event that the dielectric coating or phosphor on which the latent electrostatic image is developed is capable itself of use as a spirit master surface, the developed image can be set directly on the surface of the dielectric writing medium for subsequent use as a spirit master from which multiple copies can be produced. Instead, in the preferred practice, the latent electrostatic image is developed by the powder mixture and then a spirit master 16 is positioned with the coated side in surface contact with the developed image 18 to effect transfer of the power mixture from the dielectric Writing medium 12 or electret to the surface of the plate 16. The transfer may be effected by the step of reversing the charge from the dielectric medium to the master whereby the developing composition is preferentially attracted to the corresponding portions of the master. Alternatively, the transfer may be effected by preferential adhesion of the developing composition for the master when the latter is pressed into surface contact with the dielectric coatmg.

Corresponding results cannot be secured when the spirit soluble dyestuff is dissolved in the carnauba or other waxy medium which is thereafter reduced to finely divided form for use as the developing powder.

Instead of making use of a dry powder, the physical mixture of Example 1 can be suspended in a suitable liquid carrier wherein the liquid is characterized by low dielectric constant and an electrical resistance sufiicient to permit leakage of charge from the solid particles of dyestutf and thermoplastic material and wherein the liquid component can be selected of the class of materials such as chlorinated hydrocarbons, chlorinated-fluorinated hydrocarbons, aliphatic hydrocarbons, aromatic hydrocarbons, aromatic petroleum solvents, as represented by the following:

Boiling point, F.

Chlorinated hydrocarbons: (50% distillation) Methylene chloride 104 Ethylene dichloride 182 Trichlorethylene 186 Perchloroethylene 245 Chlorinated fluorinated hydrocarbons:

Trichloromonofluoromethane (Freon 1 l or MF) 74.8 Trichlorotrifluoroethane (Freon 113 or TF) 117.6 Tetrachlorodifiuoroethane (Freon BF) 199.0

Aliphatic hydrocarbons:

Skellysolve ASkelley Oil Co. N. pentane 91 Skellysolve BN-hexana 150 N-hexane 155 Cyclohexane 176 Skellysolve CN-heptane 201 Heptane 205 Iso-octane-Z,2,2-trimethylpentane 212 V M & P naphtha 260 DT 230 Big Ben Chemicals & Solvent 261 HiFlashV M & P naphtha 280 Solvent 429Big Ben Chemicals & Solvents 291 Napoleum 85Deep Rock Oil Co. 302 Espesol 280Signal Oil Co. 311 Espesol 310ASignal Oil Co. 318 RCS SolventCommerce Petroleum Co. 319 DT 250Big Ben Chemicals & Solvent 322 Espesol 300ASignal Oil Co. 333 Solvosol 5Socony Vacuum Oil Co 348 Stoddard Solvent 349 Boiling point, F.

(50% distillation) Deodorized Apco 125Commerce Petroleum Co. AkylacCommerce Petroleum Co.

Boiling point, F.

Aromatic hydrocarbons: (50% distillation) In the foregoing formulation, the dry solids are suspended in the liquid carrier in an amount within the range of 0.2 to 3 percent by Weight.

The wax component has sufiicient binding power to eliminate the need to heat and set the image although conventional heating techniques can be employed to reduce the wax to an adhesive stage. In addition, the wax component enjoys sufficient bonding power to hold the spirit soluble dye particles in the imaged layer that is formed on the master, either by entrapment or bonding, or by attraction of the dye particles to the surfaces of the wax. Instead of carnauba wax, use can be made of other waxes such as ceresin wax, parafiin wax, petroleum wax and the like, or use can be made of natural or synthetic resins such as polyethylene, polypropylene, coumarone indene, polystyrene and the like which exhibit good selfbonding properties or which preferably are selected to be thermoplastic to enable adhesion in response to heat.

It is desirable to make use of a mixture in which the solids contain as high a concentration of dyestutf as possible consistent with the ability of the applied layer to be retained as a permanent image 20 on the surface of the spirit master. Thus it is difiicult to make use of a physical mixture containing more than 75 parts by weight of the spirit soluble dyestuff per 25 parts by Weight of the wax and the like material, but it is desirable to make use of the dyestutf in an amount greater than 5 parts by weight per parts by weight of the wax component, although less than 5 :percent can be used when it is desirable to reproduce only a few copies.

Instead of crystal violet, use can be made of other spirit soluble dyestuffs such as methyl violet, rhodamine, Victoria blue, Victoria green, aura'mine, triphenylmethane dyes, and dye bases, and azo dyes.

In practice, after the image 20 has been set on the spirit master 16, the imaged master can be mounted in a conventional spirit duplicating machine for the production of multiple copies by bringing the copy sheets into surface contact with the image on the master While the contacting surfaces of the copy sheets are wet with water and/or alcohol to leach some of the dyestutf from the imaged master to the copy sheets to produce copy.

Formation of the electrostatic image into an imaged master for spirit duplication in the manner described has been found to improve the image quality of the electrophotocopying process since the grain structure of the latent electrostatic image is wiped out by the complete coverage obtained by the spirit copy.

Similarly, it is but a simple matter to produce multiple copies from the spirit master whereby the combination of electro-photographic reproduction from an original and spirit copy operates to provide a high speed multiple copy process with which copies of an original can be quickly and exactly reproduced. The combination also operates to provide a high speed copy process and an inexpensive copy process wherein copy is secured at high speed and with high quality on inexpensive paper.

It will be understood that changes may be made in the details of formulation and operation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. In the method for producing an imaged spirit master from which multiple copies can be produced, the steps of contacting a dielectric layer having a latent electrostatic image with a developing composition the solids of which comprise a physical mixture of a thermoplastic material capable of acquiring a charge opposite that of the latent electrostatic image in finely divided form and a spirit soluble dyestuff in finely divided form, in which the dyestufl? constitutes at least about 5 percent by weight of the mixture, said thermoplastic particles and dyestutr' being retained by electrical attraction to the latent electrostatic image while the remainder of the dielectric surface remains free of developing composition, bringing a spirit master into surface contact with the developed side of the dielectric layer, and transferring the developing composition from the dielectric'al layer to the surface of the spirit master to define the image thereon, and then setting the developing composition on the spirit master.

' 2. The method as claimed in claim 1 in which the dielectric layer is formed of a photo-conductive material in which the layer is on a conductive base.

3. The method as claimed in claim 1 in which the thermoplastic material comprises a wax.

4. The method as claimed in claim 3 in which the wax is carnauba wax.

5. The method as claimed in claim 1 in which the spirit soluble dyestufi is crystal violet.

6. The method as claimed in claim 1 in which the ent in the ratio of 1 part by Weight dyestuff to /2 to 30 parts by weight of the thermoplastic material.

7. The method as claimed in claim 1 in which the transfer of the developed image from the dielectric coating to the master is effected by the step of reversing the charge from the dielectric medium to the master whereby the developing composition is preferentially attracted to the corresponding portions of the master.

8. The method as claimed in claim 1 in which the transfer of the developing composition from the dielectric coating to the master is effected by preferential adhesion of the developing composition for the master when the latter is pressed into surface contact with the dielectric coating.

References Cited by the Examiner UNITED STATES PATENTS 78,842 6/1868 Starr et al 106-241 X 2,109,592 3/1938 Macht et al. 26041 2,297,691 10/1942 Carlson 117-37 2,309,522 1/1943 Marks 26041 2,343,781 3/1944 Locke 260-41 2,618,384 11/1952 Hatfield 26041 2,770,608 11/1956 Barker et al. 260-41 2,810,653 10/1957 Ranson 106-272 2,837,437 6/1958 Finlayson et a1 260-416 2,891,911 6/1959 Mayer et al 11717.5 X 3,010,842 11/1961 Ricker 25262.1 X 3,013,890 12/1961 Bixby 25262.1 X 3,034,428 5/1962 Ellarn et al. 8-2.5 X 3,043,684 7/1962 Mayer et al. 117-37 3,049,077 8/1962 Damm 1l7137 3,165,420 1/1965 Tomanek et al 11717.5 3,198,649 8/1965 Metcalfe et al 25262.1

T WILLIAM D. MARTIN, Primary Examiner. spirit soluble dye and the thermoplastic material are presa G. L. HUBBARD, M. SOFOCLEOUS,

Assistant Examiners. 

1. IN THE METHOD FOR PRODUCING AN IMAGED SPIRIT MASTER FROM WHICH MULITIPLE COPIES CAN BE PRODUCED, THE STEPS OF CONTACTING A DIELECTRIC LAYER HAVING A LATENT ELECTROSTATIC IMAGE WITH A DEVELOPING COMPOSITION THE SOLIDS OF WHICH COMPRISE A PHYSICAL MIXTURE OF A THERMOPLASTIC MATERIAL CAPABLE OF ACQUIRING A CHARGE OPPOSITE THAT OF THE LATENT ELECTROSTATIC IMAGE IN FINELY DIVIDED FORM AND A SPIRIT SOLUBLE DYESTUFF IN FINELY DIVIDED FORM, IN WHICH THE DYESTUFF CONSTITUTES AT LEAST ABOUT 5 PERCENT BY WEIGHT OF THE MIXTURE, SAID THERMOPLASTIC PARTICLES AND DYESTUFF BEING RETAINED BY ELECTRICAL ATTRACTION TO THE LATENT ELECTROSTATIC IMAGE WHILE THE REMAINDER OF THE DIELECTRIC SURFACE REMAINS FREE OF DEVELOPING COMPOSITION, BRINGING A SPIRIT MASTER INTO SURFACE CONTACT WITH THE DEVELOPED SIDE OF THE DIELECTIRC LAYER, AND TRANSFERRING THE DEVELOPING COMPOSITION FROM THE DIELECTRICAL LAYER TO THE SURFACE OF THE SPIRIT MASTER TO DIFINE THE IMAGE THEREON, AND THEN SETTLING THE DEVELOPING COMPOSITION ON THE SPIRIT MASTER. 